As a matter of fact this idea is not new. In the late 1970s (or perhaps very early eighties) C.Boyer, the French astronomer who discovered the 4 Day rotation of the atmosphere of Venus, published a paper in l’Astronomie mentioning that certain changes in velocity of markings during the course of the Venusian day could be due to the greater activity of life forms in the clouds.
Of course at cloud top level temperature and pressure are quite modest and carbon dioxide still plentiful…… Camille Flammarion would have been keen on this idea, being a great promoter of the concept of Universal life, originally stated by Fontenelle.